On Finite Element Approximation of the Gradient for Solution of Poisson Equation

Abstract

A nonconforming mixed finite element method is presented for approximation of ∇w with Δw=f,w| r =0. Convergence of the order∥∇w−uh∥0,Ω=O(h2) is proved, when linear finite elements are used. Only the standard regularity assumption on triangulations is needed.